Laura Bush has helped plan and design nearly every aspect of the George W. Bush Presidential Center, down to the Texas pecan timber that will panel the building’s interior walls.

But getting her first look inside the unfinished facility, the former first lady was still surprised — overwhelmed, even — by the center’s size and scope.

“You can see how really beautiful it’s going to be, but also how big and magnificent it’s going to be,” Laura Bush said.

Laura and former President George W. Bush toured the center for the first time Sunday ahead of Monday’s “topping out” ceremony at Southern Methodist University. The couple shared the milestone, which marks the final crossbeam being installed on top of the building, with invited guests and key members of the design and construction team.

The celebration Monday was also the media’s only chance to peek inside the center before its planned opening in the spring of 2013.

The project, while on schedule and under budget, is visibly a long way from that grand opening. The building’s signature red bricks, meant to mimic SMU’s Georgian-style architecture, cover only a fraction of the exterior. Inside, concrete-block walls remained largely unadorned.

But it was still apparent that the facility — which will include the museum, library, archives, policy institute, gift shop and cafes — will indeed be Texas-sized.

The lantern-like light tower at the center of the building stands 60 feet tall. There will be 20-foot-high LED screens, flashing images from Bush’s eight years as president, in the building’s entrance hall. The archives will house 42,000 artifacts, 70 million pages of documents and nearly 200 million emails.

Most striking, though, is the mammoth permanent exhibition gallery.

On Monday, the space was empty, save for a 22-foot piece of World Trade Center steel. Nearby was the center’s scale replica Oval Office, which seemed unexpectedly small by comparison. And just outside was the yet-to-be constructed Texas Rose Garden.

“After the intense experience of the 9/11 exhibit, in particular, and then the dignity of the office, probably visitors will welcome some time of relative quiet,” said New York-based architect Robert Stern, who led Monday’s hardhat tour.

Bush Center officials also revealed some of the library’s thematic elements.

Rather than being chronological, the library will be organized around principles important to the Bushes, such as freedom, responsibility, opportunity and compassion. And officials promised an open telling of the Bush presidency.

They said that will be especially visible in exhibits such as a reconstruction of Bush’s actual White House Situation Room and an interactive room called the Decision Points Theater.

“Visitors will be able to come in, choose a scenario and make a decision as the president had to make decisions,” said Alan Lowe, director of the Bush Presidential Library.

Laura Bush also emphasized the center’s Lone Star State connections, from prairie plants meant to evoke the Bushes’ Crawford ranch to limestone from the Permian Basin. She even teased her husband about all the Texas accents.

“He didn’t even realize we had a stone out there in West Texas that would work like this,” she said with a grin.

That relaxed atmosphere permeated the Monday celebration, a contrast to the more formal groundbreaking in November.

George Bush, wearing his shirt open collar, nodded and pointed at friends in the audience. He played to the crowd, calling SMU’s recent victory over rival Texas Christian University a sign of a “budding football power.”

He made fun of himself, joking about his use of a “big word” after saying there would be a “symbiotic relationship” between the center and SMU.

But on the center’s aim and mission — particularly with the Bush Institute, the center’s policy arm — the Bushes were passionate and serious. They lauded efforts already under way. And the former president promised he and Laura would pour their “heart and soul” into the center.

“The challenge is, after you’ve been president, is to make sure you’re still constructive, that you add something to society,” George Bush said.

“Politics was interesting. It was a fascinating 14 years. I’m out,” he said. “But I’m also interested in staying involved in public policy that will be consequential, that will be effective.”

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